Hong Kong said on Saturday a surge in imported cases of coronavirus would likely lead to a community outbreak and pile pressure on the city's already stretched healthcare system.
The government also said it would postpone university entrance exams until April 24.
The Chinese-ruled territory, with 273 confirmed cases of coronavirus and four deaths, is trying to contain a surge in cases as people return from overseas infected with the disease.
"The influx of people returning from overseas will last at least two weeks ... The recent epidemic caused by imported cases is much more severe than any period of combating the pandemic in the past two months," Hong Kong leader Carrie Lam said.
"It is more difficult to handle and (will) most likely lead to a large and continuous community outbreak."
Hong Kong has toughened curbs on travelers, ordering 14 days of quarantine for arrivals from midnight on Thursday and advising against all non-essential travel.
The government said it would make civil servants work from home and urged employers to be flexible with work from home arrangements.
Schools would remain closed until further notice, it added.